The present invention relates to the fluid dispensing arts. It finds particular application in conjunction with rigid dispensers for liquid detergents susceptible to contamination by airborne microorganisms and other biological matter, and will be described with particular reference thereto. It should be appreciated, however, that the invention is also applicable to the dispensing of other liquids for which airborne contamination is undesirable, such as liquid food concentrates and in medical applications.
Liquid dispensers are widely used for dispensing discrete quantities or charges of detergents, soaps, germicides and other viscous liquid and semi-solid materials. Frequently, the container of liquid is inserted into a wall-mounted housing. Liquid is released in discrete amounts from a nozzle by depression of a lever or other dispensing mechanism.
As fluid is dispensed from the rigid container, a slight vacuum is created and air is drawn into the container, thereby returning the pressure to atmospheric and allowing further amounts of fluid to be dispensed. A simple method of venting the container involves making a small aperture in the container, usually in an upper, fluid free, portion, to allow air to enter without the risk of escape of the fluid through the aperture. This type of venting arrangement is disclosed, for example, in U.S. Pat. No. 4,673,109 to Cassia.
To prevent leakage from the aperture during transit, and contamination or drying of the fluid contents, the vent aperture is either pierced immediately prior to use or formed during manufacture and sealed for transportation.
End user vents are usually formed by puncturing the container manually with any suitable tool such as a punch, awl, or pocket knife. Manufactured vent apertures are usually drilled or molded into the container then sealed in one of a number of ways. One method is to insert a plug into the aperture before filling the container. The plug is removed by the end user prior to use. To prevent leakage around the plug, or loss of the plug during transit, the aperture is precisely drilled. Another method of sealing is to apply an adhesive cover tab over the aperture prior to filling the container, as disclosed, for example, in U.S. Pat. No. 4,673,109 to Cassia. Problems arise, however, if the adhesive used is incompatible with the product and loss of adhesion occurs.
As an alternative to an aperture in the wall of the container, U.S. Pat. No. 4,646,945 to Steiner, et al. discloses a vent mechanism in a closure for a container. A check valve allows air in but prevents product from flowing out. The vent mechanism, however, is expensive to manufacture because of the number and tolerance of the parts.
All the venting methods described above cause unfiltered air to enter the container during dispensing of the product. Air entering the container through the open vent aperture or check valve contains bioburden such as microorganisms and other contaminants. In many cases the product is susceptible to degradation by the bioburden or provides a medium for growth of harmful microorganisms. Contact between the product and the bioburden is particularly enhanced in the case of the check valve, where air entering the container bubbles through the product before collecting in the head space, increasing the susceptibility of the product to the bioburden. Tools used to puncture the container mechanically also introduce bioburden to the product in variable amounts.
Preservatives added to the product counteract the effects of the bioburden to a certain degree but are sometimes overwhelmed by the nature or volume of bioburden entering through the vent. In some cases, preservatives, or significant quantities thereof, are incompatible with the end use of the product and their use is therefore limited.
As a result, a number of systems have been developed for filtering the air to remove bioburden before the air enters the container. In one system, a depression molded into the container includes an aperture at the base of the depression. A filter is inserted into the depression prior to filling the container with product. In use, the filter allows microbe filtered air to enter the container. During transit, however, product frequently passes through the vent aperture and comes into contact with the filter. Air tends to cause the product to dry on the filter, plugging the filter before the container is put into service. This prevents air from entering through the aperture, interfering with the dispensing of the product or encouraging unfiltered air to enter the container through the dispensing mechanism.
In an advancement on the filter system described, U.S. Pat. No. 5,439,144 to Holzner discloses a plug, inserted into the aperture before filling, which prevents the product from coming into contact with the filter during transit. As before, the aperture is in a molded depression in the container, with a filter inserted into the depression. The end user pushes the plug through the aperture, allowing filtered air to enter the container. However, to prevent leakage around the plug, a precisely drilled aperture, rather than a molded aperture is used. The additional parts and assembly considerably increase the cost of the mechanism.
The present invention provides a new and improved filtered venting system for liquid containers which overcomes the above-referenced problems and others.